JPWO2014163138A1 - Base station and processor - Google Patents

Abstract

The base station which concerns on embodiment is a base station which communicates with the user terminal in an own cell. The base station controls a handover of the user terminal to an adjacent base station before setting a power saving communication mode in which communication with the user terminal is performed in a state where power consumption of the base station is reduced Is provided.

Description

  The present invention relates to a base station used in a mobile communication system.

  In 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, an energy saving technique for reducing power consumption of a base station is introduced (for example, see Non-Patent Document 1). For example, the power consumption of the base station can be reduced by stopping the operation of the base station cell at night when communication traffic is low.

3GPP Technical Specification “TS36.300 V11.4.0” December 2012

  However, by stopping the operation of the cell of the base station, power saving of the base station is realized, but communication with the user terminal becomes impossible in the cell. Therefore, it has been difficult to realize energy saving while suppressing deterioration in service quality.

  Therefore, the present invention provides a base station that can realize energy saving while suppressing degradation of service quality.

  The base station which concerns on a 1st characteristic communicates with the user terminal in an own cell. The base station controls a handover of the user terminal to an adjacent base station before setting a power saving communication mode in which communication with the user terminal is performed in a state where power consumption of the base station is reduced Is provided.

  The base station which concerns on a 2nd characteristic communicates with the user terminal in an own cell. A plurality of types of power saving communication modes differing in the method for reducing the power consumption of the base station are defined. The base station includes a control unit that notifies an adjacent base station of information indicating at least one of a type and setting of a power saving communication mode selected from the plurality of types of power saving communication modes.

  The base station according to the present invention can realize energy saving while suppressing deterioration in service quality.

FIG. 1 is a configuration diagram of an LTE system according to the first embodiment. FIG. 2 is a block diagram of the UE according to the first embodiment. FIG. 3 is a block diagram of the eNB according to the first embodiment. FIG. 4 is a protocol stack diagram of a radio interface in the LTE system. FIG. 5 is a configuration diagram of a radio frame used in the LTE system. FIG. 6 is a diagram illustrating an operating environment according to the first embodiment. FIG. 7 is a diagram for explaining intermittent transmission according to the first embodiment. FIG. 8 is a diagram for explaining the reduction of the number of transmission antennas according to the first embodiment. FIG. 9 is a sequence diagram of an operation pattern 1 according to the first embodiment. FIG. 10 is a sequence diagram of an operation pattern 2 according to the first embodiment. FIG. 11 is a sequence diagram of an operation pattern 3 according to the first embodiment. FIG. 12 is a flowchart of the power saving communication mode selection process according to the first embodiment. FIG. 13 is a diagram for explaining an eNB Configuration Update message according to the first embodiment. FIG. 14 is a diagram for explaining an eNB Configuration Update message according to the first embodiment. FIG. 15 is a diagram for explaining a Cell Activation Request message according to the first embodiment. FIG. 16 is a diagram for explaining the Cell Activation Request message according to the first embodiment. FIG. 17 is a sequence diagram of an operation pattern according to the second embodiment.

[Outline of Embodiment]
The base station according to the embodiment performs communication with user terminals in the own cell. The base station includes a control unit that controls handover of the user terminal to before setting a power saving communication mode in which communication with the user terminal is performed in a state where power consumption of the base station is reduced.

  In the embodiment, the control unit controls handover of the user terminal to the adjacent base station based on QoS required for communication with the user terminal.

  In the embodiment, the control unit sets the power saving communication mode after performing the handover when the QoS cannot be satisfied when the power saving communication mode is set.

  In the embodiment, the control unit includes information indicating handover for the power saving communication mode in a handover request transmitted to the adjacent base station in the handover procedure.

  In the embodiment, the control unit sets the power saving communication mode in response to the base station receiving the setting request for the power saving communication mode from the adjacent base station.

  In the embodiment, a plurality of types of power saving communication modes different in the method of reducing the power consumption of the base station are defined. The setting request includes information indicating at least one of a type and setting of the power saving communication mode required for the base station.

  In the embodiment, the control unit transmits an inquiry as to whether or not the power saving communication mode is permitted to an adjacent base station. The control unit sets the power saving communication mode in response to the base station receiving a positive response to the inquiry from the adjacent base station.

  In the embodiment, a plurality of types of power saving communication modes different in the method of reducing the power consumption of the base station are defined. The inquiry includes information indicating at least one of the type and setting of the power saving communication mode scheduled by the base station.

  In the embodiment, the inquiry includes information indicating a communication capacity required for the adjacent base station by setting the power saving communication mode and / or information indicating a number of user terminals under the base station. .

  In the embodiment, when the power saving communication mode is set, the control unit transmits a completion notification indicating that the power saving communication mode is set to the adjacent base station.

  In the embodiment, a plurality of types of power saving communication modes different in the method of reducing the power consumption of the base station are defined. The completion notification includes information indicating at least one of the type and setting of the power saving communication mode set by the base station.

  In the embodiment, the information indicating the setting of the power saving communication mode includes at least one of a system frame number and a subframe number to which the power saving communication mode is applied.

  In the embodiment, the information indicating the setting of the power saving communication mode is, in the adjacent base station, a radio resource in a subframe indicated by the subframe number or a subframe configuring a frame indicated by the sysrem frame number. It is used to allocate an MCS having a data rate equal to or higher than a predetermined value to the user terminal to which a radio resource is allocated.

  In the embodiment, a plurality of types of power saving communication modes different in the method of reducing the power consumption of the base station are defined. A power saving communication mode to be set by the base station is selected from the plurality of types of power saving communication modes based on a predetermined priority order or a communication capacity of the base station.

  The base station according to the embodiment performs communication with user terminals in the own cell. A plurality of types of power saving communication modes differing in the method for reducing the power consumption of the base station are defined. The base station includes a control unit that notifies an adjacent base station of information indicating at least one of a type and setting of a power saving communication mode selected from the plurality of types of power saving communication modes.

  The base station according to the embodiment further includes a reception unit that receives a setting request for requesting setting of a power saving communication mode from the plurality of types of power saving communication modes from the adjacent base station. The control unit selects the power saving communication mode from the plurality of types of power saving communication modes. The control unit notifies the information to the neighboring base station that has transmitted the setting request.

  In the embodiment, the control unit requests the adjacent base station to control the setting of the power saving communication mode in the base station. The receiving unit receives the setting request from the neighboring base station that has received a response to accept the request.

  In the embodiment, the receiving unit receives a request from the adjacent base station that the adjacent base station controls the setting of the power saving communication mode in the base station. The receiving unit receives the setting request from the adjacent base station when the control unit transmits a response indicating that the request is accepted to the adjacent base station.

  In the embodiment, the control unit maintains a list in which the neighboring base stations that control the setting of the power saving communication mode in the base station are recorded. The control unit notifies the adjacent base station of the information based on the list.

  In the embodiment, the setting request is a power-saving communication mode to be set by the base station from the plurality of types of power-saving communication modes, while maintaining the coverage of the base station and an upper limit of the processing load of the base station It includes information requesting a mode that keeps the value below a predetermined value.

  In the embodiment, the setting request is information indicating at least one of a time to start the power saving communication mode, a time to end the power saving communication mode, and a timer value indicating a setting period of the power saving communication mode. including.

  In the embodiment, when the predicted processing capacity of the base station assuming that the power saving communication mode is set according to the setting request is lower than the processing capacity currently requested by the base station, An inquiry about whether to set the power saving communication mode according to the setting request is sent to the neighboring base station.

[First Embodiment]
Hereinafter, an embodiment in which the present invention is applied to LTE (Long Term Evolution) standardized by 3GPP will be described with reference to the drawings.

(Configuration of LTE system)
FIG. 1 is a configuration diagram of an LTE system according to the first embodiment. 1, the LTE system includes a plurality of UEs (User Equipment) 100, an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 10, and an EPC (Evolved Packet Core) 20. The E-UTRAN 10 corresponds to a radio access network, and the EPC 20 corresponds to a core network. The E-UTRAN 10 and the EPC 20 constitute an LTE system network.

  The UE 100 is a mobile communication device, and performs wireless communication with a connection destination cell (serving cell). UE100 is corresponded to a user terminal.

  The E-UTRAN 10 includes a plurality of eNBs 200 (evolved Node-B). The eNB 200 corresponds to a base station. The eNB 200 manages one or a plurality of cells, and performs radio communication with the UE 100 that has established a connection with the own cell. Note that “cell” is used as a term indicating a minimum unit of a radio communication area, and is also used as a term indicating a function of performing radio communication with the UE 100.

  The eNB 200 has, for example, a radio resource management (RRM) function, a user data routing function, and a measurement control function for mobility control and scheduling.

  The EPC 20 includes a plurality of MME (Mobility Management Entity) / S-GW (Serving-Gateway) 300. The MME is a network node that performs various types of mobility control for the UE 100, and corresponds to a control station. The S-GW is a network node that performs transfer control of user data, and corresponds to an exchange. EPC20 comprised by MME / S-GW300 accommodates eNB200.

  The eNB 200 is connected to each other via the X2 interface. Moreover, eNB200 is connected with MME / S-GW300 via S1 interface.

  Next, configurations of the UE 100 and the eNB 200 will be described.

  FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100 includes a plurality of antennas 101, a radio transceiver 110, a user interface 120, a GNSS (Global Navigation Satellite System) receiver 130, a battery 140, a memory 150, a processor 160, Have. The memory 150 and the processor 160 constitute a control unit. The UE 100 may not have the GNSS receiver 130. Further, the memory 150 may be integrated with the processor 160, and this set (that is, a chip set) may be used as the processor 160 '.

  The plurality of antennas 101 and the wireless transceiver 110 are used for transmitting and receiving wireless signals. Radio transceiver 110 includes a transmission unit 111 that converts a baseband signal (transmission signal) output from processor 160 into a radio signal and transmits the radio signal from a plurality of antennas 101. The radio transceiver 110 includes a reception unit 112 that converts radio signals received by the plurality of antennas 101 into baseband signals (reception signals) and outputs the baseband signals to the processor 160.

  The user interface 120 is an interface with a user who owns the UE 100, and includes, for example, a display, a microphone, a speaker, and various buttons. The user interface 120 receives an operation from the user and outputs a signal indicating the content of the operation to the processor 160. The GNSS receiver 130 receives a GNSS signal and outputs the received signal to the processor 160 in order to obtain location information indicating the geographical location of the UE 100. The battery 140 stores power to be supplied to each block of the UE 100.

  The memory 150 stores a program executed by the processor 160 and information used for processing by the processor 160. The processor 160 includes a baseband processor that modulates / demodulates and encodes / decodes a baseband signal, and a CPU (Central Processing Unit) that executes programs stored in the memory 150 and performs various processes. . The processor 160 may further include a codec that performs encoding / decoding of an audio / video signal. The processor 160 executes various processes and various communication protocols described later.

  FIG. 3 is a block diagram of the eNB 200. As illustrated in FIG. 3, the eNB 200 includes a plurality of antennas 201, a radio transceiver 210, a network interface 220, a memory 230, and a processor 240. The memory 230 and the processor 240 constitute a control unit. The memory 230 may be integrated with the processor 240, and this set (that is, a chip set) may be used as the processor.

  The plurality of antennas 201 and the wireless transceiver 210 are used for transmitting and receiving wireless signals. The radio transceiver 210 includes a transmission unit 211 that converts a baseband signal (transmission signal) output from the processor 240 into a radio signal and transmits the radio signal from the plurality of antennas 201. The radio transceiver 210 includes a reception unit 212 that converts radio signals received by the plurality of antennas 201 into baseband signals (reception signals) and outputs the baseband signals to the processor 240.

  The network interface 220 is connected to the neighboring eNB 200 via the X2 interface and is connected to the MME / S-GW 300 via the S1 interface. The network interface 220 is used for communication performed on the X2 interface and communication performed on the S1 interface.

  The memory 230 stores a program executed by the processor 240 and information used for processing by the processor 240. The processor 240 includes a baseband processor that performs modulation / demodulation and encoding / decoding of a baseband signal, and a CPU that executes a program stored in the memory 230 and performs various processes. The processor 240 executes various processes and various communication protocols described later.

  FIG. 4 is a protocol stack diagram of a radio interface in the LTE system. As shown in FIG. 4, the radio interface protocol is divided into layers 1 to 3 of the OSI reference model, and layer 1 is a physical (PHY) layer. Layer 2 includes a MAC (Media Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer. Layer 3 includes an RRC (Radio Resource Control) layer.

  The physical layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data is transmitted between the physical layer of the UE 100 and the physical layer of the eNB 200 via a physical channel.

  The MAC layer performs data priority control, retransmission processing by hybrid ARQ (HARQ), and the like. Data is transmitted via the transport channel between the MAC layer of the UE 100 and the MAC layer of the eNB 200. The MAC layer of the eNB 200 includes a scheduler that determines uplink / downlink transport formats (transport block size, modulation / coding scheme (MCS)) and allocated resource blocks.

  The RLC layer transmits data to the RLC layer on the receiving side using functions of the MAC layer and the physical layer. Data is transmitted between the RLC layer of the UE 100 and the RLC layer of the eNB 200 via a logical channel.

  The PDCP layer performs header compression / decompression and encryption / decryption.

  The RRC layer is defined only in the control plane. Control messages (RRC messages) for various settings are transmitted between the RRC layer of the UE 100 and the RRC layer of the eNB 200. The RRC layer controls the logical channel, the transport channel, and the physical channel according to establishment, re-establishment, and release of the radio bearer. If there is an RRC connection between the RRC of the UE 100 and the RRC of the eNB 200, the UE 100 is in a connected state (RRC connected state), and otherwise, the UE 100 is in an idle state (RRC idle state).

  A NAS (Non-Access Stratum) layer located above the RRC layer performs session management, mobility management, and the like.

  FIG. 5 is a configuration diagram of a radio frame used in the LTE system. In the LTE system, OFDMA (Orthogonal Frequency Division Multiplexing Access) is applied to the downlink and SC-FDMA (Single Carrier Frequency Multiple Access) is applied to the uplink.

  As shown in FIG. 5, the radio frame is composed of 10 subframes arranged in the time direction, and each subframe is composed of two slots arranged in the time direction. The length of each subframe is 1 ms, and the length of each slot is 0.5 ms. Each subframe includes a plurality of resource blocks (RB) in the frequency direction and includes a plurality of symbols in the time direction. The resource block includes a plurality of subcarriers in the frequency direction. Among radio resources allocated to the UE 100, a frequency resource can be specified by a resource block, and a time resource can be specified by a subframe (or slot).

  In the downlink, the section of the first few symbols of each subframe is a control region mainly used as a physical downlink control channel (PDCCH) for transmitting a control signal. The remaining section of each subframe is an area that can be used as a physical downlink shared channel (PDSCH) mainly for transmitting user data.

  In the uplink, both ends in the frequency direction in each subframe are control regions mainly used as a physical uplink control channel (PUCCH) for transmitting a control signal. Further, the central portion in the frequency direction in each subframe is an area that can be used as a physical uplink shared channel (PUSCH) mainly for transmitting user data.

(Operation according to the first embodiment)
(1) Outline of Operation FIG. 6 is a diagram showing an operating environment according to the present embodiment. As shown in FIG. 6, pico eNB (PeNB) 200-2 and 200-3 are installed in the coverage of the macro eNB (MeNB) 200-1. That is, MeNB200-1 and PeNB200-2 are adjacent to each other, and MeNB200-1 and PeNB200-3 are adjacent to each other.

  MeNB200-1 manages a large cell (macro cell). Each of the PeNBs 200-2 and 200-3 manages a small cell (pico cell). Moreover, UE100 is located in the coverage of PeNB200-2, and UE100 is connected with PeNB200-2. An X2 interface is established between the MeNB 200-1 and the PeNB 200-2 and between the MeNB 200-1 and the PeNB 200-3. An X2 interface may also be established between PeNBs 200-2 and 200-3.

  In the present embodiment, a plurality of types of power saving communication modes that differ in the method of reducing the power consumption of the eNB 200 are defined. The power saving communication mode is a mode in which communication with the UE 100 is performed in a state where the power consumption of the eNB 200 is reduced. Hereinafter, the power saving communication mode is appropriately referred to as a “partial OFF mode”. Details of the power saving communication mode will be described later.

  In the operating environment illustrated in FIG. 6, it is assumed that the PeNB 200-2 sets the power saving communication mode. When the PeNB 200-2 sets the power saving communication mode, the communication capacity and / or communication quality in the PeNB 200-2 deteriorates, so that QoS (Quality of Service) required for communication of the UE 100 may not be satisfied. QoS refers to delay time, throughput (bandwidth), jitter, and the like.

  In the present embodiment, the PeNB 200-2 sets the neighbor cell (MeNB 200-1) based on the QoS required for communication with the UE 100 (hereinafter referred to as “request QoS”) before setting the power saving communication mode. The handover of the UE 100 is controlled. Specifically, the PeNB 200-2 sets the power saving communication mode after performing the handover of the UE 100 when the requested QoS cannot be satisfied when the power saving communication mode is set. Thereby, the energy saving of PeNB200-2 is realizable, suppressing the fall of service quality. In addition, if the requested QoS is satisfied even if the power saving communication mode is set, the signaling and processing load can be suppressed by not performing the handover of the UE 100.

  In the operation pattern 1, the PeNB 200-2 sets the power saving communication mode in response to the PeNB 200-2 receiving a request for setting the power saving communication mode (Partial OFF Request) from the MeNB 200-1. Thereby, MeNB200-1 initiative can set the power saving communication mode of PeNB200-2.

  In the operation pattern 2, the PeNB 200-2 transmits an inquiry (Partial OFF Inquiry) as to whether or not the power saving communication mode is permitted to the MeNB 200-1. The PeNB 200-2 sets the power saving communication mode in response to the PeNB 200-2 receiving from the MeNB 200-1 an acknowledgment (Partial OFF Response) to the inquiry (Partial OFF Inquiry). Thereby, PeNB200-2 initiative can set the power saving communication mode of PeNB200-2.

  However, the PeNB 200-2 may set the power saving communication mode without receiving a request or permission from the MeNB 200-1 (operation pattern 3).

  In the present embodiment, the PeNB 200-2 includes information indicating that it is a handover for the power saving communication mode (that is, energy saving) in the handover request transmitted to the MeNB 200-1 in the handover procedure. Thereby, MeNB200-1 can perform the judgment which considered the necessity of the power saving communication mode, when judging whether a handover request is accepted.

  In this embodiment, when the power saving communication mode is set, the PeNB 200-2 transmits a completion notification (Partial OFF Complete) indicating that the power saving communication mode is set to the MeNB 200-1. Thereby, MeNB200-1 can recognize that PeNB200-2 exists in a power saving communication mode.

  The PeNB 200-2 may also perform signaling to the PeNB 200-3. For example, the PeNB 200-2 may transmit a completion notification (Partial OFF Complete) indicating that the power saving communication mode has been set to the PeNB 200-3.

(2) Power-saving communication mode As described above, in this embodiment, a plurality of types of power-saving communication modes differing in the method for reducing the power consumption of the eNB 200 are defined.

  The types of power saving communication modes include “Discontinuous Transmission (DTX)”, “Reduction of Number of Transmission Antennas (ANT reduced)”, “Reduction of Transmission Power (TxPower reduced)”, and “Reduction of Processing Capacity (Capacity reduced)”. and so on.

  The intermittent transmission is a power saving communication mode in which the eNB 200 intermittently transmits a radio signal. FIG. 7 is a diagram for explaining intermittent transmission according to the present embodiment. As illustrated in FIG. 7, the eNB 200 intermittently transmits a cell-specific reference signal (CRS). In the example of FIG. 7, the CRS is transmitted once every 5 subframes. The eNB 200 sets a transmission stop period (DTX period) in a period (subframe) in which CRS is not transmitted. In the transmission stop period, since power supply to the transmission unit 211 (particularly, the power amplifier) of the eNB 200 can be stopped, energy saving can be realized.

  The reduction in the number of transmission antennas is a power saving communication mode in which the number of antennas used by the eNB 200 for transmitting radio signals (hereinafter referred to as “number of used antennas”) is reduced. FIG. 8 is a diagram for explaining a reduction in the number of transmission antennas according to the present embodiment. As illustrated in FIG. 8, the eNB 200 transmits a radio signal using only a part of the plurality of antennas 201. By reducing the number of used antennas, the power consumption of the eNB 200 (particularly, the transmission unit 211) is reduced, so that energy saving can be realized.

  The transmission power reduction is a power saving communication mode in which the eNB 200 reduces transmission power and performs redundant transmission of transmission data using surplus radio resources. By reducing the transmission power, the power consumption of the eNB 200 (particularly, the transmission unit 211) is reduced, so that energy saving of the eNB 200 can be realized.

  The processing capacity reduction is a power saving communication mode in which the upper limit value of the processing capacity of the eNB 200 is kept below a predetermined value while maintaining the coverage of the eNB 200. Here, the predetermined value is not a value set so as not to exceed the limit of the processing capability of the processor 240, but a value set lower than the limit of the processing capability of the processor 240. By performing such a restriction, it is possible to suppress a decrease in service quality while reducing the power consumption of the eNB 200 (particularly, the processor 240).

  One type of processing capacity reduction is communication capacity reduction. The communication capacity reduction is a power saving communication mode in which the number of UEs that can be connected to the eNB 200 or the amount of radio resources that can be allocated by the eNB 200 is limited. By performing such a restriction, power consumption of the eNB 200 (particularly, the processor 240) is reduced, so that energy saving of the eNB 200 can be realized.

  As a method of keeping the processing load of the eNB 200 below a predetermined value while maintaining the coverage of the eNB 200, for example, a method of limiting the number of UEs connectable to the eNB 200 described above, a method of limiting the number of UEs to be processed simultaneously, and a change in scheduling algorithm There is a method for reducing the amount of calculation. The number of UEs to be processed simultaneously includes the number of UEs to be scheduled and the number of UEs to be controlled.

  In addition, in order to maintain the coverage of the eNB 200, the reception function of the radio transceiver 210 of the eNB 200 is in a receivable state (or a state in which intermittent reception is possible).

(3) Operation Sequence Next, the operation sequence according to the present embodiment will be described in the order of operation patterns 1 to 3.

(3.1) Operation pattern 1
FIG. 9 is a sequence diagram of the operation pattern 1 according to the present embodiment. In operation pattern 1, energy saving of PeNB 200-2 is performed under the initiative of MeNB 200-1. In an initial state, UEs 100-1 and 100-2 are connected to PeNB 200-2.

  As illustrated in FIG. 9, in step S101, the MeNB 200-1 determines whether to perform energy saving of the PeNB 200-2. This determination is performed according to any of the following first determination method to third determination method.

  As a first determination method, the MeNB 200-1 determines that the PeNB 200-2 is based on the time variation of the traffic situation (the number of connected UEs, the amount of transmitted / received data, or the radio resource usage rate) in the MeNB 200-1 and / or the PeNB 200-2. Determine whether to perform energy saving. For example, the MeNB 200-1 determines to perform energy saving of the PeNB 200-2 in a time zone with a small amount of transmission / reception data. Alternatively, the MeNB 200-1 determines to perform energy saving for the PeNB 200-2 when the number of connected UEs of the PeNB 200-2 falls below the threshold.

  As a second determination method, the MeNB 200-1 determines whether or not to perform energy saving of the PeNB 200-2 based on an instruction (energy saving ON / OFF command) from an OAM (Operation and Maintenance).

  As a third determination method, the MeNB 200-1 determines whether to perform energy saving based on the power supply status of the MeNB 200-1 or the power supply status of the PeNB 200-2. If the MeNB 200-1 is notified of the power supply status of the PeNB 200-2, the MeNB 200-1 can grasp the power supply status of the PeNB 200-2. For example, when the power supply of the PeNB 200-2 is interrupted (when the battery is driven), the MeNB 200-1 is when the remaining battery level of the PeNB 200-2 falls below a specified value, or the private power generation of the PeNB 200-2 When the output power of (e.g., solar) falls below a specified value, it is determined that energy saving of PeNB 200-2 is performed.

  Next, in step S102, the MeNB 200-1 transmits a power saving communication mode setting request (Partial OFF Request) to the PeNB 200-2. The setting request (Partial OFF Request) includes information indicating at least one of the type and setting of the power saving communication mode required for the PeNB 200-2. The setting of the power saving communication mode is, for example, an intermittent transmission pattern (such as an activation cycle of the transmission unit 211 or a transmission stop subframe number (or transmission stop system frame number)) if the type of the power saving communication mode is intermittent transmission. If the type of the power saving communication mode is a reduction in the number of transmission antennas, the number of transmission antennas (or the number of antennas to be stopped) is used.

  In step S103, PeNB200-2 calculates the communication capacity of the own cell at the time of setting the requested | required power saving communication mode according to reception of the setting request | requirement (Partial OFF Request).

  In step S104, PeNB200-2 confirms each request | requirement QoS of UE100 (UE100-1 and 100-2) in an own cell. The requested QoS is determined based on, for example, QCI (Quality Class Identifier) corresponding to the radio bearer established by the UE.

  In step S105, the PeNB 200-2 determines whether or not to perform the handover of the UE 100 in the own cell depending on whether or not the requested QoS can be satisfied when the requested power saving communication mode is set. If the requested QoS cannot be satisfied when the power saving communication mode is set, it is determined that the UE 100 that does not satisfy the requested QoS is to be handed over. Here, the description will be made assuming that it is determined that the UE 100-1 is to be handed over.

  In step S106, the PeNB 200-2 transmits setting information (Measurement Config.) For instructing measurement of the reception state (reception power and / or reception quality) to the UE 100-1.

  In step S107, the UE 100-1 performs measurement for the serving cell (PeNB200-2) and the neighboring cell (MeNB200-1) based on the setting information (Measurement Config.), And reports a measurement result (Measurement Report) to the PeNB200-2. Send to.

  In step S108, PeNB200-2 determines the hand-over destination of UE100-1 based on the measurement result report (Measurement Report) from UE100-1. Here, the description will be made assuming that MeNB 200-1 is the handover destination.

  In step S109, the PeNB 200-2 transmits a handover request to the MeNB 200-1.

  In step S110, the MeNB 200-1 determines whether to accept the handover request. Here, the description will be made assuming that it is determined that the handover request is accepted. The handover request may include information indicating that the handover is for the power saving communication mode (that is, energy saving).

  In step S111, the MeNB 200-1 transmits an acknowledgment (ACK) to the handover request to the PeNB 200-2.

  In step S112, PeNB200-2 transmits the instruction | indication (Handover Command) of the hand-over to MeNB200-1 to UE100-1 according to reception of an acknowledgment (ACK).

  In step S113, the UE 100-1 performs handover to the MeNB 200-1 in response to reception of the handover instruction (Handover Command). And UE100-1 establishes a connection with MeNB200-1 by a hand-over (step S114).

  In step S115, the PeNB 200-2 sets the requested power saving communication mode (Partial OFF).

  In step S116, the PeNB 200-2 transmits a completion notification (Partial OFF Complete) indicating that the power saving communication mode has been set to the MeNB 200-1. The completion notification (Partial OFF Complete) may include information indicating at least one of the type and setting of the power saving communication mode set by the PeNB 200-2.

  Thus, by notifying the type and setting of the power saving communication mode between the eNBs 200, the MeNB 200-1 can perform appropriate control in consideration of the type and setting of the power saving communication mode of the PeNB 200-2. . For example, when PeNB200-2 is performing intermittent transmission (DTX) in which transmission is stopped in a specific subframe (or a specific frame), MeNB200-1 is in the specific subframe (or the specific frame). An MCS having a high data rate (that is, a predetermined value or more) can be assigned to the UE 100 under its control. For example, the MeNB 200-1 can assign an MCS with a modulation scheme of 64QAM to the UE 100 in the specific subframe. In addition, the MeNB 200-1 can perform an appropriate measurement setting (Measurement Config.) For the UE 100 under its control in consideration of the type and setting of the power saving communication mode of the PeNB 200-2.

(3.2) Operation pattern 2
FIG. 10 is a sequence diagram of an operation pattern 2 according to the present embodiment. The operation pattern 2 is a pattern for performing energy saving of the PeNB 200-2 led by the PeNB 200-2. In an initial state, UEs 100-1 and 100-2 are connected to PeNB 200-2. Note that description overlapping with the operation pattern 1 is omitted as appropriate.

  As shown in FIG. 10, in step S201, the PeNB 200-2 determines whether or not to perform its own energy saving. This determination is performed according to any of the following first determination method to third determination method.

  As a first determination method, the PeNB 200-2 uses the energy saving of the PeNB 200-2 based on the time variation of the traffic situation (the number of connected UEs in the cell, the amount of transmitted / received data, or the radio resource usage rate) in the own cell. It is determined whether or not to perform. Specifically, it is determined that energy saving is performed in a time zone in which traffic (amount of transmitted / received data) is small.

  As a second determination method, the PeNB 200-2 determines whether or not to perform energy saving based on an instruction (energy saving ON / OFF command) from an OAM (Operation and Maintenance).

  As a third determination method, the MeNB 200-1 determines whether to perform energy saving based on the power supply status of the MeNB 200-1 or the power supply status of the PeNB 200-2. If the PeNB 200-2 is notified of the power supply status of the MeNB 200-1, the PeNB 200-2 can grasp the power supply status of the MeNB 200-1. For example, when the power supply of the PeNB 200-2 is cut off (when the battery is driven), if the remaining battery level of the PeNB 200-2 falls below a specified value, the self-generated electric power (solar power etc.) is the specified value. It is determined that energy saving is performed when the value is lower than.

  In step S202, the PeNB 200-2 transmits an inquiry (Partial OFF Inquiry) as to whether or not the power saving communication mode is permitted to the MeNB 200-1. The inquiry (Partial OFF Inquiry) includes information indicating the communication capacity required of the MeNB 200-1 by setting the power saving communication mode. Alternatively, the inquiry (Partial OFF Inquiry) includes information indicating at least one of the type and setting of the power saving communication mode scheduled by the PeNB 200-2.

  The inquiry (Partial OFF Inquiry) may include information indicating the number of UEs under the control of the PeNB 200-2. Thereby, MeNB200-1 can implement the judgment which considered the acceptance | permission acceptance decision | availability of handover, and the number of affected UEs.

  The PeNB 200-2 may start a timer when an inquiry (Partial OFF Inquiry) is transmitted, and may inquire again when the timer exceeds a certain time.

  In step S203, the MeNB 200-1 transmits an acknowledgment (Partial OFF Response) to the PeNB 200-2 in response to the inquiry (Partial OFF Inquiry). The acknowledgment (Partial OFF Response) may include information indicating the communication capacity (surplus capacity) of the MeNB 200-1.

  In step S204, the PeNB 200-2 transmits setting information (Measurement Config.) For instructing measurement of the reception state (reception power and / or reception quality) to each of the UEs 100-1 and 100-2.

  In step S205, each of the UEs 100-1 and 100-2 performs measurement on the serving cell (PeNB200-2) and the neighboring cell (MeNB200-1) based on the setting information (Measurement Config.), And reports the measurement result (Measurement). Report) is transmitted to PeNB 200-2.

  In step S206, PeNB200-2 determines each handover destination (candidate) of UE100-1 and 100-2 based on the measurement result report (Measurement Report) from each of UE100-1 and 100-2. . Here, the description will be made assuming that MeNB 200-1 is determined as the handover destination (candidate).

  In step S207, PeNB200-2 confirms each request | requirement QoS of UE100-1 and 100-2.

  In step S208, the PeNB 200-2 determines whether to perform the handover of the UE 100-1 and / or 100-2 depending on whether the requested QoS can be satisfied when the power saving communication mode is set. PeNB200-2 may confirm whether request | requirement QoS can be satisfied based on the communication capacity of an own cell and / or the communication capacity of an adjacent cell (MeNB200-1). For example, when the power saving communication mode is set, when the UE 100-1 determines that the requested QoS is not satisfied in the own cell, the MeNB 200-1 satisfies the requested QoS, and the UE 100-1 is handed over to the MeNB 200-1 to decide.

  In step S209, the PeNB 200-2 transmits a handover request to the MeNB 200-1. The PeNB 200-2 includes information indicating that it is a handover for the power saving communication mode (energy saving) in the handover request.

  In step S210, the MeNB 200-1 determines whether to accept the handover request. Here, the description will be made assuming that it is determined that the handover request is accepted. The subsequent procedure (steps S211 to S214) is the same as that of the operation pattern 1.

  In this sequence, steps S204 and S205 may be performed before step S202. Thereby, the inquiry (Partial OFF Inquiry) can be performed after clarifying the handover destination of the UE 100 and calculating the necessary communication capacity.

(3.3) Operation pattern 3
FIG. 11 is a sequence diagram of the operation pattern 3 according to the present embodiment.

  The operation pattern 3 is different from the operation pattern 2 in that the PeNB 200-2 sets the power saving communication mode without making an inquiry to the MeNB 200-1, but the other procedures (steps S301 to S313) are the same as the operation pattern 2. However, in the operation pattern 3, the PeNB 200-2 may include information indicating at least one of the type and setting of the power saving communication mode in the handover request (step S307).

(4) Power saving communication mode selection process In step S101, step S201, and step S301 described above, a predetermined priority order, or processing capacity / communication capacity of PeNB 200-2 (and / or MeNB 200-1) ( Based on (capacity), the power saving communication mode to be set by the PeNB 200-2 is selected. The order of priority may be the order in which interference with adjacent cells is reduced, or the order in which the coverage of the own cell is not affected.

  Moreover, the power saving communication mode may be applied after sequentially estimating the communication capacity when the power saving communication mode is applied according to the priority order and confirming that the requested QoS is satisfied.

  Alternatively, the power saving communication mode may be applied according to the priority order, and the power saving communication mode may be reselected if the communication capacity at that time is greatly reduced.

  Note that the power-saving communication mode may be (re) selected with the start or end of communication with the UE 100 as a trigger.

  FIG. 12 is a flowchart of power saving communication mode selection processing. Here, a case where the power saving communication mode is selected in the order of reducing interference will be described. Moreover, PeNB200-2 performs selection of a power saving communication mode.

  As illustrated in FIG. 12, the PeNB 200-2 determines whether to apply in the order of intermittent transmission (DTX), transmission antenna number reduction (ANT reduced), processing capacity reduction (Capacity reduced), and transmission power reduction (TxPower reduced). To do. Specifically, the PeNB 200-2 applies intermittent transmission (step S401), and applies a reduction in the number of transmission antennas if the communication capacity is sufficient (or if further power saving is necessary) (step S401). S402, S403).

  Further, if there is a margin in communication capacity (or if further power saving is necessary) even if the number of transmission antennas is reduced, communication capacity reduction (processing capacity reduction) is applied (steps S404 and S405).

  Further, if there is a margin in the communication capacity even if the communication capacity reduction is applied (or if further power saving is necessary), the transmission power reduction is applied (steps S406 and S407).

  Note that, when the power saving communication mode is used in combination with the communication stop mode (a mode in which communication with the UE 100 is not performed), the communication stop mode may be finally applied.

(5) Message Configuration Example The above-mentioned X2 is used to send the above-described power saving communication mode setting notification (Partial OFF Complete), power saving communication mode setting request (Partial OFF Request), power saving communication mode inquiry (Partial OFF Inquiry). It may be an information element of a message.

  13 and 14 are diagrams for explaining the eNB Configuration Update message according to the present embodiment. As illustrated in FIG. 13, the eNB Configuration Update message is a kind of X2 message, and is mainly a message for notifying the neighboring eNB 200 of a setting change in the eNB 200. As illustrated in FIG. 14, the eNB Configuration Update message according to the present embodiment includes information related to a power saving communication mode setting notification (Partial OFF Complete).

  FIG.15 and FIG.16 is a figure for demonstrating the Cell Activation Request message which concerns on this embodiment. As illustrated in FIG. 15, the Cell Activation Request message is a kind of X2 message, and is mainly a message for the eNB 200 to request the neighboring eNB 200 to start a cell. As illustrated in FIG. 16, the Cell Activation Request message according to the present embodiment includes information related to a power saving communication mode setting request (Partial OFF Request).

[Second Embodiment]
Next, a second embodiment will be described. In addition, it demonstrates centering around a different part from the above-mentioned embodiment, and abbreviate | omits description for the same part suitably.

(1) Outline of Operation An outline of operation according to the present embodiment will be described.

  In the first embodiment described above, the case of performing the energy saving of the PeNB 200-2 led by the MeNB 200-1 (operation pattern 1) and the case of performing the energy saving of the PeNB 200-2 led by the PeNB 200-2 (operation pattern 2) have been described. However, in the present embodiment, a case will be described in which energy saving of the slave eNB (Slave-eNB) 200-4 is performed under the initiative of the master eNB (Master-eNB) 200-3.

  Here, master eNB200-3 is eNB200 which controls the energy saving of slave eNB200-4. Therefore, the relationship between the master eNB 200-3 and the slave eNB 200-4 may be not only the relationship between the MeNB 200-1 and the PeNB 200-2 but also the relationship of the same eNB 200. In the present embodiment, the relationship between the master eNB 200-3 and the slave eNB 200-4 is a relationship between adjacent eNBs. An X2 interface is established between the master eNB 200-3 and the slave eNB 200-4.

  Further, regarding the determination of the master eNB 200-3 and the slave eNB 200-4, the eNBs 200 may negotiate to determine the master eNB 200-3 and the slave eNB 200-4.

  For example, the eNB 200-4 requests the eNB 200-3 to control the power saving communication mode setting in the eNB 200-4. That is, the eNB 200-4 requests the eNB 200-3 to become the master eNB 200-4. The eNB 200-3 determines whether to accept the request from the eNB 200-4. When the eNB 200-3 determines to accept the request from the eNB 200-4, the eNB 200-3 transmits a response indicating that the request from the eNB 200-4 is accepted to the eNB 200-4. When the eNB 200-4 receives the response, the relationship between the master eNB 200-3 and the slave eNB 200-4 is established.

  Or eNB200-3 requests | requires that eNB200-3 controls the setting of the power saving communication mode in eNB200-4 with respect to eNB200-4. That is, eNB200-3 requests | requires that eNB200-4 becomes slave eNB200-4. The eNB 200-4 determines whether to accept the request from the eNB 200-3. When the eNB 200-4 determines to accept the request from the eNB 200-3, the eNB 200-4 transmits a response to accept the request from the eNB 200-2 to the eNB 200-3. When the eNB 200-3 receives the response, the relationship between the master eNB 200-3 and the slave eNB 200-4 is established.

  Note that the request from the eNB 200-3 or the eNB 200-4 may include its own cell size (for example, transmission power). The eNB 200-3 or eNB 200-4 that has received the request may compare its own cell size (for example, transmission power) with the cell size of the transmission source of the request and determine whether to accept the request. Good. Moreover, eNB200-3 or eNB200-4 may judge whether the said request | requirement is accepted based on the master / slave eNB information which shows whether the neighboring eNB200 is the master eNB200 or the slave eNB200. For example, when the other neighboring eNB 200 is already the master eNB 200 in the eNB 200-4, it may be determined that the request from the eNB 200-3 is rejected, and the eNB 200-3 is also the master eNB 200-3 with respect to the other eNB 200. In some cases, it may be determined that the request from the eNB 200-4 is accepted. Note that the master / slave eNB information may be recorded in an adjacent cell list held by the eNB 200 or may be recorded in a dedicated table. The eNB 200-3 and the eNB 200-4 may exchange the dedicated table (for example, when the dedicated table is updated).

  As described above, by determining the master eNB 200-3 and the slave eNB 200-4 by negotiation between the eNBs 200, energy saving in cooperation between the SON and the eNB is possible.

  Moreover, not only the negotiation between eNB200 but master eNB200-3 and slave eNB200-4 may be determined by the instruction | indication from a high-order network (for example, OAM).

(2) Operation Sequence Next, an operation sequence according to the second embodiment will be described with reference to FIG. FIG. 17 is a sequence diagram of an operation pattern according to the second embodiment.

  As illustrated in FIG. 17, in step S501, the master eNB 200-3 determines whether to perform energy saving of the slave eNB 200-4. This determination is performed according to the determination method in step S101 of the operation pattern 1.

  In step S502, the master eNB 200-3 transmits a power saving communication mode setting request to the slave eNB 200-4. Specifically, the master eNB 200-3 transmits, to the slave eNB 200-4, a setting request (Capacity-reduced Mode Request) including information indicating the setting of processing capacity reduction as the power saving communication mode. The slave eNB 200-4 receives the setting request.

  In the present embodiment, the setting request includes setting information (Capacity-reduced Config.) For setting processing capacity reduction. Examples of the setting information include the upper limit number of UEs to be processed simultaneously, the time when the power saving communication mode starts, the time when the power saving communication mode ends, a timer value indicating the setting period of the power saving communication mode, and the like.

  In step S503, the slave eNB 200-4 calculates the expected processing capacity C1 of the slave eNB 200-4 when it is assumed that the requested power saving communication mode is set according to the setting request.

  In step S504, the slave eNB 200-4 calculates the requested processing capability C2 that is currently requested by the slave eNB 200-4. For example, the slave eNB 200-4 calculates the request processing capacity based on the number of connected UEs of the slave eNB 200-4.

  In step S505, the slave eNB 200-4 determines whether or not the predicted processing capacity C1 is lower than the requested processing capacity C2. Slave eNB200-4 performs the process of step S506, when the estimated processing capacity C1 is less than the request processing capacity C2 (in the case of "Yes"). On the other hand, the slave eNB 200-4 executes the process of step S509 when the predicted processing capacity C1 is not lower than the requested processing capacity C2 (in the case of “No”).

  In step S506, the slave eNB 200-4 transmits an inquiry (Capacity Inquiry) as to whether or not to set the power saving communication mode according to the setting request to the master eNB 200-3. The master eNB 200-3 receives the inquiry.

  The inquiry may include information indicating the predicted processing capacity C1 and the requested processing capacity C2.

  In response to receiving the inquiry, the master eNB 200-3 determines whether to set the power saving communication mode according to the setting request.

  In step S507, the master eNB 200-3 transmits, to the slave eNB 200-4, a determination result (Capacity Response) as to whether or not to set the power saving communication mode as a response to the inquiry. The slave eNB 200-4 receives the determination result.

  The determination result includes information indicating that the power saving communication mode is set or not set according to the setting request. In addition, the determination result may include information indicating that another power saving communication mode is set together with information indicating that the power saving communication mode is not set according to the setting request.

  Note that the master eNB 200-3 may transmit a new power saving communication mode setting request instead of the determination result.

  In step S508, the slave eNB 200-4 determines whether or not to set the power saving communication mode based on the determination result. Slave eNB200-4 performs the process of step S509, when setting a power saving communication mode (in the case of "Yes"), and complete | finishes a process, when not setting a power saving communication mode (in the case of "No"). .

  In step S509, the slave eNB 200-4 performs the power saving communication mode according to the setting request. In the present embodiment, the slave eNB 200-4 sets the processing capacity reduction mode.

  In step S510, the slave eNB 200-4 transmits state update information (Status update) to the master eNB 200-3. The master eNB 200-3 receives the state update information.

  The state update information includes information on setting of the power saving communication mode, an upper limit number (max # of UEs) of UEs to be simultaneously processed in the set power saving communication mode, and a threshold (timer threshold) regarding the end time of the power saving communication mode. Information indicating at least one of them is included. The thresholds related to the end time of the power communication mode include a time when the power saving communication mode is ended, a timer value indicating the setting period of the power saving communication mode (expired value of the setting timer), and the like.

  In the present embodiment, the state update information includes information indicating that the processing capacity reduction mode has been set.

  Note that the slave eNB 200-4 may transmit the state update information not only to the master eNB 200-3 but also to an upper network (for example, OAM), the MeNB 200, the neighboring eNB 200, and the like.

  In step S511, the slave eNB 200-4 starts a power saving communication mode setting timer (recovery timer).

  In step S512, the slave eNB 200-4 determines whether the setting timer has expired. Slave eNB200-4 performs the process of step S513, when the setting timer expires (in the case of "Yes"), and repeats the process of step S512 when the setting timer has not expired (in the case of "No"). .

  In step S513, the slave eNB 200-4 ends the power saving communication mode. In the present embodiment, the slave eNB 200-4 cancels the setting of the processing capacity reduction mode.

  In step S514, the slave eNB 200-4 transmits state update information to the master eNB 200-3. The master eNB 200-3 receives the state update information. In the present embodiment, the state update information includes information indicating that the normal mode has been set.

[Other Embodiments]
In the above-described embodiment, it is assumed that the handover destination candidate from the PeNB 200-2 is only the MeNB 200-1, but when there are a plurality of handover destination candidates, the capability or category (number of antennas, etc.) of the UE 100 is set. It is desirable to determine an appropriate handover destination in consideration.

  In the second embodiment described above, the eNB 200 (specifically, the PeNB 200-2) determines whether the requested QoS can be satisfied when the requested power saving communication mode is set. Although it has been determined whether or not to perform the handover of the UE 100, the handover may be determined based not only on the requested QoS but also on the basis of RSRP (Reference Signal Received Power) or / and RSRQ (Reference Signal Received Quality). . For example, the eNB 200 may determine whether or not to perform a handover of the UE 100 based on the requested QoS after determining whether or not the RSRP or / and RSRQ of the eNB 200 is less than the threshold. Thereby, UE100 located in the edge part of an own cell can be made into the object of a handover preferentially. In addition, when the number of UEs in the own cell exceeds the threshold, the eNB 200 may determine handover based on not only the requested QoS but also RSRP or / and RSRQ. In addition, when the requested power saving communication mode is set, the eNB 200 performs handover based on RSRP or / and RSRQ when the requested QoS of at least one UE among all the UEs 100 in the own cell cannot be satisfied. The target UE 100 may be determined. Moreover, eNB200 may determine UE100 whose request | requirement QoS is high and RSRP or / and RSRQ are less than a threshold value as the object UE100 of handover.

  In addition to the power saving communication mode described in the above-described embodiment, the following methods 1) to 3) may be employed.

  1) Use of MBSFN or ABS: MBSFN (MBMS Single Frequency Network) subframe or ABS (Almost Blank Subframe) is set, and transmission is stopped in the subframe.

  2) Use of TDD DwPTS in Special Subframe: A method in which the DwPTS in the Special Subframe included in the radio frame in the case of TDD is set to the minimum time and transmission is stopped outside the DwPTS time.

  3) Use of TDD dynamic frame configuration: A method in which a setting that minimizes the downlink transmission subframe is performed in the TDD frame setting (config.), And transmission is stopped in the uplink time.

  In 1st Embodiment mentioned above, although the power saving communication mode was set to PeNB, you may set a power saving communication mode to MeNB.

  In the above-described embodiment, the MeNB 200-1 and the PeNB 200-2 may determine whether to end the setting of the power saving communication mode according to the determination criterion regarding whether to perform the energy saving described above. For example, the MeNB 200-1 determines to end the setting of the power saving communication mode of the PeNB 200-2 when the number of connected UEs of the PeNB 200-2 exceeds a threshold value. When the power saving communication mode is set, the PeNB 200 uses information for determining whether to end the setting of the power saving communication mode as a periodic or predetermined trigger (for example, power saving communication). May be transmitted to the MeNB 200-1 according to the case where the mode setting criterion is not satisfied.

  In the second embodiment described above, the slave eNB 200-4 transmits state update information. However, the slave eNB 200-4 may transmit state update information in response to a request or inquiry from the master eNB 200-3.

  In step S505 of the second embodiment described above, if the expected processing capacity C1 is lower than the requested processing capacity C2, whether to perform handover of the UE 100 in the own cell based on the requested QoS and / or RSRP or / and RSRQ It may be determined whether or not.

  In the second embodiment described above, the slave eNB 200-4 has finished setting the power saving communication mode after the setting timer has expired, but is not limited thereto. The slave eNB 200-4 may determine whether or not to continue the setting of the power saving communication mode according to the determination criterion as to whether or not to perform energy saving according to the first embodiment.

  The operations of the master eNB 200-3 and the slave eNB 200-4 in the second embodiment described above may be appropriately performed by the MeNB 200-1 and the PeNB 200-2 in the above-described embodiment. Or operation of MeNB200-1 and PeNB200-2 in embodiment mentioned above may perform suitably master eNB200-3 and slave eNB200-4. Therefore, for example, when the power saving communication mode is set, the PeNB 200-2 may transmit the above-described state update information to the MeNB 200-1.

  Moreover, although the heterogeneous network configuration including MeNB and PeNB was assumed, other network configurations may be used.

  In the embodiment described above, the case where the present invention is applied to the LTE system is mainly described. However, the present invention is not limited to the LTE system, and the present invention may be applied to a system other than the LTE system.

  Note that the entire contents of Japanese Patent Application No. 2013-080002 (filed on April 5, 2013) and Japanese Patent Application No. 2013-224466 (filed on October 29, 2013) are incorporated herein by reference. Built in.

  As described above, the base station according to the present invention is useful in the mobile communication field because it can realize energy saving while suppressing deterioration in service quality.

Claims (22)

A base station that communicates with user terminals in its own cell,
A control unit that controls handover of the user terminal to an adjacent base station before setting a power saving communication mode in which communication with the user terminal is performed in a state where power consumption of the base station is reduced. Base station.   The base station according to claim 1, wherein the control unit controls handover of the user terminal to the adjacent base station based on QoS required for communication with the user terminal.   The base station according to claim 2, wherein the control unit sets the power saving communication mode after performing the handover when the QoS cannot be satisfied when the power saving communication mode is set. .   The base unit according to claim 3, wherein the control unit includes information indicating handover for the power saving communication mode in a handover request transmitted to the neighboring base station in the handover procedure. Bureau.   The base unit according to claim 1, wherein the control unit sets the power saving communication mode in response to the base station receiving the setting request for the power saving communication mode from the neighboring base station. Bureau. A plurality of types of power-saving communication modes differing in the method for reducing the power consumption of the base station are defined,
The base station according to claim 5, wherein the setting request includes information indicating at least one of a type and a setting of the power saving communication mode required for the base station. The control unit transmits an inquiry as to whether or not the power saving communication mode is permitted to an adjacent base station,
The base station according to claim 1, wherein the control unit sets the power saving communication mode in response to the base station receiving an affirmative response to the inquiry from the adjacent base station. A plurality of types of power-saving communication modes differing in the method for reducing the power consumption of the base station are defined,
The base station according to claim 7, wherein the inquiry includes information indicating at least one of a type and a setting of the power saving communication mode scheduled by the base station.   The inquiry includes information indicating a communication capacity required for the adjacent base station by setting the power saving communication mode and / or information indicating a number of user terminals under the base station. The base station according to claim 7.   The base station according to claim 1, wherein, when the power saving communication mode is set, the control unit transmits a completion notification indicating that the power saving communication mode is set to the neighboring base station. . A plurality of types of power-saving communication modes differing in the method for reducing the power consumption of the base station are defined,
The base station according to claim 10, wherein the completion notification includes information indicating at least one of a type and setting of the power saving communication mode set by the base station.   The base station according to claim 11, wherein the information indicating the setting of the power saving communication mode includes at least one of a system frame number and a subframe number to which the power saving communication mode is applied.   The information indicating the setting of the power saving communication mode is the radio resource in the subframe indicated by the subframe number or the radio resource in the subframe constituting the frame indicated by the sysrem frame number in the adjacent base station. The base station according to claim 12, wherein the base station is used to allocate an MCS having a data rate equal to or higher than a predetermined value to the user terminal to which is allocated. A plurality of types of power-saving communication modes differing in the method for reducing the power consumption of the base station are defined,
A power saving communication mode to be set by the base station is selected from the plurality of types of power saving communication modes based on a predetermined priority order or a communication capacity of the base station. The base station according to claim 1. A base station that communicates with user terminals in its own cell,
A plurality of types of power-saving communication modes differing in the method for reducing the power consumption of the base station are defined,
The base station includes a control unit that notifies an adjacent base station of information indicating at least one of a type and setting of a power saving communication mode selected from the plurality of types of power saving communication modes. base station. A receiver that receives a setting request for requesting to set a power-saving communication mode from the plurality of types of power-saving communication modes;
The control unit selects the power saving communication mode from the plurality of types of power saving communication modes,
The base station according to claim 15, wherein the control unit notifies the information to the neighboring base station that has transmitted the setting request. The control unit requests the neighboring base station to control the setting of the power saving communication mode in the base station to the neighboring base station,
The base station according to claim 16, wherein the receiving unit receives the setting request from the neighboring base station that has received a response indicating that the request is accepted. The receiving unit receives a request from the neighboring base station that the neighboring base station controls the setting of the power saving communication mode in the base station;
The base unit according to claim 16, wherein the receiving unit receives the setting request from the adjacent base station when the control unit transmits a response to the request to accept the request to the adjacent base station. Bureau. The control unit maintains a list in which the neighboring base stations that control the setting of the power saving communication mode in the base station are recorded,
The base station according to claim 16, wherein the control unit notifies the neighboring base station of the information based on the list.   The setting request is a power-saving communication mode to be set by the base station among the plurality of types of power-saving communication modes, and an upper limit value of the processing load of the base station is set to a predetermined value while maintaining the coverage of the base station. The base station according to claim 16, comprising information requesting a mode to be suppressed to less than the base mode.   The setting request includes information indicating at least one of a time to start the power saving communication mode, a time to end the power saving communication mode, and a timer value indicating a setting period of the power saving communication mode. The base station according to claim 16, characterized in that:   When the predicted processing capacity of the base station when the power saving communication mode is set according to the setting request is less than the processing capacity currently requested by the base station, the control unit follows the setting request. The base station according to claim 16, wherein an inquiry as to whether or not to set the power saving communication mode is sent to the adjacent base station.

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